Using Database Dump for backups is a bad idea.  Use SQL backup, it's much, much, faster and safer, too.

If you've coded for the creation of a session, you can add the vba code to an Excel or Access file, calling your procedure on open.  Alternatively, compiling an exe in VB6 would also make it easier to schedule.  

Option 2: https://www.orchid.systems/product/process-scheduler

Option 3: As Jay indicated, scheduling backups via SQL is a better option.  It's not that difficult at all.

Also, have a look at the Productivity/Backup category on 3rdParty.info for a list of available Sage 300 backup tools.